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In this paper we report on the numerical analysis of convection patterns - due to changes in humidity - of air inside a two-dimensional square enclosure. The enclosure, with dimensions of 10 cm by 10 cm, and atmospheric air as the working fluid, is placed in a horizontal position with the gravitational force acting directly downward on it. Thermally, the system and its boundaries are at a constant temperature of 20°C, whereas the humidity varies with position inside the cavity. At the top and bottom walls, the relative humidity is set at 0 and 1, respectively, while the vertical walls are considered as impermeable. The mathematical model is based on two-dimensional versions of the conservation equations for mass, momentum and moisture, in Cartesian coordinates, under laminar flow and steady-state conditions. The governing equations were discretized and solved over the computational domain with the Finite Element method for different system conditions. The results, given in terms of velocity, density and humidity fields, show that convection patterns form as a result of buoyancy forces generated by humidity gradients, just as they do in thermal convection. Further comparison to the thermal convection process of dry air on the same system, show that the two are closely related.